In electronic vehicle control systems, it is occasionally necessary to develop a boost voltage potential which is greater than the vehicle battery voltage. This boost voltage is typically utilized in providing an initial high pull-in current for engine fuel injectors. Boost voltage can also be utilized to supply a required higher than battery voltage drive signal for FET transistors which have their drain electrode connected to battery voltage such that the gate drive voltage must be higher than battery voltage to insure turning on the FET. The present invention is related to a boost voltage power supply which efficiently and economically develops a higher than battery voltage boost voltage potential, and the use of such a boost voltage power supply in a vehicle control system.
Typically, the larger than battery voltage boost voltage is developed by circuits which utilize an additional capacitive or inductive reactance to store energy and then utilize rectification circuits to retrieve this stored energy at appropriate times so as to develop a higher than battery voltage boost voltage potential. In such circuits, it is typically necessary to provide an additional relatively large and expensive capacitive or inductive reactance to store the energy to be utilized for developing the boost voltage. This is in addition to any storage capacitance which may be utilized to maintain the developed boost voltage potential. Thus, typically solenoid drivers for fuel injection systems utilize a separate additional coil for energy storage so as to develop a boost voltage potential which is applied to fuel injectors to enhance the response time of these injectors during an initial pull-in period.
In some prior systems, the inductance of the fuel injector solenoid is used to develop boost voltage. However, in these prior systems, developing boost voltage only occurs at the end of an effective on logic state of the solenoid, and this limits the availability and magnitude of the developed boost voltage since boost voltage is only replenished at the end of each effective on state of the solenoid.